1986 pickup z24 engine runs rough

[masdbo]

Just purchased an 86 pickup with z24 engine that runs like the plug wires are on wrong..... first thing I checked and they seem to be right as per the diagrams... Previously owner, replaced distributor, plugs, wires, cap and rotor. I pretty much gave up but considered it might be the pcm... I just got the truck and haven't really got into it yet. Any suggestions?
Thanks

[Rev_D21]

Welcome to NICO. Could be as simple as a brittle vacuum hose that collapsed. Be sure to download the 1989 truck FSM (89 and 86 are similar enough) at www.nicoclub.com/FSM. Look in the Hardbody folder. It's a large file but it's everything you ever wanted to know about your truck.

[masdbo]

I haven't had a chance to really get into it yet, but I noticed there are bad hoses up where they attach to the breather so I'm sure they are bad elsewhere. I was sure from the sound of it plug wires were on wrong, it's that rough! I will download that folder and start from there, thanks!

[masdbo]

I found that the # 3 and #4 cylinders have no compression..... about 25lbs. This motor was rebuilt about 20k ago, kinds strange valves would be burnt on both, maybe running lean on those two. Previous owner said it got worse and worse.... Are those cylinders controlled off of the same injector??
thanks

[Rev_D21]

No compression? It could be head gasket related. Pull off the valve cover, disable spark, watch the camshaft turn while someone cranks the truck over. Look for the valves in the rear two cylinders to move. One last thought, it could have holes in the piston tops. What's the history of this truck?

[masdbo]

Yea, I am thinking head gasket too.... maybe blown between the two cylinders, they have the exact compression. The valves are moving and DON'T SAY HOLES IN PISTON. I'll try to pull the head off soon and take a look. The truck has 153k on it, suposedly the engine was rebuilt around 130k. He did say it did blow a head gasket before, cause the rebuilder didn't mill the head.... Thanks

[masdbo]

ok, head off, head gasket blown between 3 and 4.... fyi
thanks